Booster device for fluid pressure system



E. R. PRICE BOOSTER DEVICE FOR FLUID PRESSURE SYSTEMS Filed March 5, 1945 Jan. 2, 1951 QQQ a Patented Jan. 2, 1951 BOOSTER DEVICE FOR FLUID PRESSURE SYSTEM Earl R. Price, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a

corporation of Delaware Application March 5, 1945, Serial No. 581,117

This invention relates to booster devices for hydraulic pressure systems, particularly hydraulic brake systems wherein the usual operator operated master cylinder and wheel cylinders or motors are provided. In such systems, the power device which provides the booster effect is usually under the control of valve mechanism, which in turn is under the control of the hydraulic pressure in the operator operated master cylinder. Heretofore this has necessitated providing, in addition to the bore for the hydraulic piston in the auxiliary master cylinder which is associated with the power device, a second bore in which reciprocates the piston which operates the valve mechanism.

An object of the present invention is to simplify and make less expensive a booster device of this type, particularly by locating the piston which controls the valve mechanism in the same bore as the piston which develops the wheel cylinder pressure. With this arrangement, the former valve pistol seal is eliminated, since the seal heretofore located at the closed end of the auxiliary master cylinder serves as the seal for the present valve, piston More Specifically, the present invention provides a valve controlling piston located in the auxiliary master cylinder acting against a laterally ofiset reaction member, such as the usual diaphragm. through the medium of a lever which proportions the effort of the piston and the reaction member in such a manner as to obtain the desired ratio between the power developed and the manual force exerted.

A further object of the present invention is to improve and simplify the construction of the piston in the auxiliary master cylinder.

Other objects and attainments of the present invention will become apparent during the following description.

In the accompanying drawing:

Figure l is a section taken through a booster unit embodying my invention, the operator operated master cylinder and the wheel cylinder being shown diagrammatically;

Figure 2 is an end view of the lever arrangement of Figure 1;

Figure 3 is a longitudinal-section of the hydraulic piston of Figure 1, taken at right angles to the sectional view of Figure 1; and

Figure 4 is a section taken on the line 4-4 of Figure 1, showing an end view of the hydraulic piston.

Referring to the drawing, a conventional master cylinder l2 operated by a pedal 14 may be 4 Claims. (Cl. 6054.5)

connected by means of a line I6 to inlet port I8 of auxiliary master cylinder 20. An outlet port 22 of cylinder 28 is connected by means of line 24 to one or more conventional motors or wheel cylinders 28.

A piston 28 is reciprocable within the bore 38 of cylinder 20, the usual seal 32 being provided to prevent inopportune passage of fluid between chamber 34 ahead of the piston and chamber 38 at the rear of the piston. The cylinder 28 is located at the front of and preferably concentric with a power device or power cylinder 38. A convenient construction of the hydraulic cylinder and power cylinder 38 is shown, wherein the forward end 40 of power cylinder 38 is formed as an integral part of the same casting which provides hydraulic cylinder 28. Th side and rear walls of power cylinder 38 may be constituted by a drawn member 42 which is secured to the cast 20 front portion 48 by means of a plurality of screws 44. The interior of power cylinder 38 is divided into two chambers 46 and 48 by means of a piston or pressure responsive movable member 50, the particular construction and arrangement of which is not material to the present invention. Preferably chamber 46 is constantly in communication with air at atmospheric pressure through a ported fitting 52, and chamber 48 is connected by means of passage 54 with control chamber 56 of a control valve generally indicated at 58. The structure and operation of valve 58 will be more fully discussed hereinafter.

Although chamber 48 of the power cylinder. as well as chamber 46, is normally maintained at atmospheric pressure, the arrangement is such that chamber 48 can be evacuated to develop a pressure differential over piston 58, which will thereupon transmit pressure through the end wall of sleeve 59 and pressure transmitting rod 62 to piston 28 in hydraulic cylinder 20, tending to move said piston 28 toward the right to develop a pressure in chamber 34 and motor 28. A crosspin 68 connects sleeve 59 to rod 62, in order to provide a positive means for returning the rod to released position.

The structure of piston 28 is shown more clearly in Figure 3. The piston comprises a forward full-diameter portion 29, a tapering portion 3|, and a rearwardly extending small-diameter portion 33. A transverse slot 35 is provided in the rear portion of the piston, and a cylindrical opening 31 in the back of the piston receives the forward end of rod 62. Pressure is transmitted from rod 52 to piston 28 primarily through a thrust washer 39, located in the bottom of the opening 81. A cross-pin 84 extends through openings in the forward end of rod 82 and in the rear portion 88 of piston 28, in order to provide a positive connection for retracting the piston 28 when the power piston is retracted. The pin 84 is retained in position by a snap-washer 88 (see Fig. 3).

In the released position of the mechanism shown in the drawing, communication between chambers 88 and 84 of cylinder 28 is permitted by a passage 88 through piston 28. A retainer or cap 81, which is carried by-the forward end of piston 28, is provided with an orifice 89 which permits liquid to flow into chamber 34; passage of liquid into chamber 84 is also permitted by the several slots II, shown in Figure 4. As seen in Figure 4, the cap 81 is held in position by means of a plurality of spaced radially extending arms I2, which extend under a retaining washer I8 (see Figures 1 and 3). Although a ball valve element 88 is urged by a spring I8 to seat at I2 and thereby cut ofi the flow of liquid through passage 88, a floating member 14 has a forwardly extending portion 18 which holds the ball away from its seat as long as piston 28 remains in retracted position, the member I4 having rearwardly extending forks I8 which rest against a washer 88 mounted in fixed position inside the cylinder bore. The rear edge of piston 28 also rests against washer 88 in released position (see Figure 3).

As soon as rod 82 is moved forwardly by power cylinder piston 58, piston 28 is moved away from washer 88, allowing a slight rearward movement of floating member I4 relative to piston 28 and thereby permitting valve 88 to close passage 88, and prevent, during the brake application, further now of liquid from chamber 84 to chamber 38. The pressure developed by the operator in master cylinder I2 is communicated to chamber 88 and therefore exerts a pressure against the rear of piston 28 which assists the power cylinder in developing brake applying pressure in motor 28.

In devices or this Klllfl, control of the operation of the power cylinder lsaccomplished by the pressure fluid or the master cylinder I2. Heretoi'orea'fiseparate piston operating in a separate bore and connected to the master cyLnder has been used for the purpose of controlling the valve mechanlsm 58, which in turn controls the operation of power cylinder 38. In the present arrangement a secondary piston 82 18 provided in the bore 38 of cylinder 28 for the purpose of controlling valve 58. The piston 82 has an opening '84- through the center thereof to accommodate rod' 82, and is provided with the usual seal 88 to prevent escape of fluid from chamber 38 past piston 82. It will be apparent that the pressure developed in master cylinder I2 and acting in chamber 36 will act against piston 82 tending to move it toward the left or toward the rear of cylinder 28.

The rear of piston 82 is in contact with portion 88 of a lever 98 which is located inside the casing of power cylinder 38 and which is pivotally mounted by means of a pin 92 on arms 94 of a bracket 98 secured to the inside front wall of the power cylinder by means of fasten ngs 98. The lever 98 may be channel-shaped in section, as shown, a slot I88 in the bottom. of the channel extending upwardly from the lower end of the lever beyond rod 62, and a second slot I82 extending downwardly from the upper end of the lever to receive a rod I84, the left end of which is threaded in order that the connection between rod I84 and lever 88 can be adjusted to compensate for manufacturing tolerances by means of a nut and lock-nut combination I88. 'Rod I84 ex tends through a seal I88 into chamber II8,of valve 58, where it is connected to a ported cage member II2 which is secured to a plate II4 providing a valve seat. Chamber II8 of the valve is constantly open to air at atmospheric pressure, and port I I8 of the valve is conne ted to a source of vacuum, such as the conve tional intake manifold.

The forces acting on lever 98 are provided by piston 82 acting in one direction and by a reaction member acting in the opposite direction to exert a force proportional to the force developed in the power cylinder against the force exerted by the operator, thereby giving the operator a sense of feel from which he can gauge the extent of brake application. This reaction is preferably provided by a diaphragm reaction member II8 laterally offset from the hydraulic cylinder 28 and mounted between that portion I28 of valve 58, which is formed, integral with cylinder 28 and the front end of the power cylinder 38, and a casting I22 which completes the valve enclosure. The diaphragm H8 in the illustrated device is annular in shape and has its inner edge secured between cage H2 and plate II4, the open center of the reaction member being closed during brake application by valve member I24 which is at that time seatedagainst plate II 4. The amount of pressure differential developed over reaction diaphragm H8 is the same as that developed over power piston 58, so that the reaction force is proportional to the force developed by the power cylinder, the ratio dependingupon the relative areas of the reaction member I I8 and piston 58, and upon the leverage relationship provided by lever 98 between reaction member H8 and piston 82. Because lever 98 is so arranged as to give a substantial leverage advantage to reaction member II8 over piston 82, the area of reaction member II8 may be relatively small, thereby reducing the overall size of the booster unit.

Although the operation of the illustrated arrangement is doubtless apparent from the foregoing description, a brief summary is believed to be in order. When the operator wishes to apply the brakes he, in the usual manner, develops a pressure in master cylinder I2 which is transmitted through conduit I8, chamber 38, passage 88, chamber 34 and conduit 24 to the motor 28, and at the same time, the pressure developed in master cylinder I2, acting against piston 82, urges lever 98 in a counterclockwise direction to draw rod I84 toward the left, lifting plate II4 from its resting place against the prongs I28. As'soon as plate II4 contacts valve member I24 communication of air at atmospheric pressure from chamber II 8 through ports I28 and chamber 88 to chamber 48 of the power cylinder is cut ofl. Further movement of plate II4 lifts valve member I24 from its seat at the end of vacuum port I I8, thereby beginning the evacuation of air from chamber 48 of the power cylinder. A pressure differential over piston 88 is thus developed which moves piston 28 forward in cylinder 28. There-.. upon valve 88 closes passage 68 and chamber 84' is sealed from chamber 38. Pressure is now developed in motor 28 according to the combined eiforts of the operator and of the power cylinder. Since chamber II8 of valve 58 and chamber 48 of the power cylinder are both connected to air at atmospheric pressure, and since chamber 88 of the valve and chamber 48 of the power cylinder are interconnected, the pressure differential developed over the reaction member H8 is the same as that developed over piston 50, and the force developed over reaction member H8 which is proportional to that developed by the power piston, acts toward the right as viewed in Figure 1, or in other words in a direction tending to move lever 90 clockwise and therefore against the pressure exerted on the lever by piston 82. Whenever the force of reaction member H8 acting through its lever arm balances the force of piston 82 acting through its lever arm, the valve will move to lapped position and thereby prevent further increase of the power cylinder effort. The valve is in lapped position when the reaction pressure on member H8 is sufl'icient to cause valve member I24 to cut off port H6, although plate H4 remains in contact with valve member,l24 and thus prevents release of the pressure in the power cylinder.

When the pressure of the operator on master cylinder I2 is released, this permits piston 82 to be forced to the right by the pressure acting on reaction member 8, and plate H4 is caused to move away from valve member I24 by the valve return spring I30. Chamber 48 of the power cylinder is thus connected to air at atmospheric pressure, and return spring I32 in the power cylinder returns both power cylinder 50 and piston 28 in hydraulic cylinder 20 to released position. Communication is re-established between chambers 34 and 3B, and the parts are therefore in their original positions, as shown in the drawmg.

Although a particular embodiment of my invention has been described, it will be understood by those skilled in the art that the object of the invention may be attained by the use of constructions different in certain respects from that disclosed without departing from the underlying principles of the invention. I therefore desire by the following claims to include within the scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A booster unit for a hydraulic brake system comprising a power cylinder having a casing and a pressure responsive member movable therein under the influence of a diiferential air pressure, a hydraulic cylinder located in front of the power cylinder and having an inlet port near its rear end adapted to be connected to an operator operated master cylinder and an outlet port at its forward end adapted to be connected to a hydraulic motor, a piston located between said inlet and outlet ports and reciprocable in said hydraulic cylinder, said piston having a passage therethrough normally permitting c0mmunication between the master cylinder and motor, a pressure transmitting rod connected to the pressure responsive member in the power cylinder and arranged to exert pressure on the piston in the hydraulic cylinder after closing the passage therein, a second piston in said hydraulic cylinder located at the rear thereof and on the opposite side of the inlet port from the first piston, the pressure of liquid entering said inlet port acting against the first piston tending to move it forwardly and against the second piston tending to move it rearwardly, said second piston having the same outer diameter as the first piston and havventing the escape of liquid past said second piston, a lever pivotallymounted on the inside of the power cylinder casing and pivotally contacting the rear of said second piston, valve means located at the front of said power cylinder but olfset laterally from the hydraulic cylinder, said valve means being arranged to control operation of said power cylinder, a connection between said lever and said valve means which enables said lever to operate said valve means and which is adjustable to vary the distance between the valve means and the part of the lever which operates the valve means, and a reaction diaphragm associated with said valve means and connected to said lever to exert a force on said lever proportional to the force developed in the power cylinder, said lever being urged in one direction by the second piston in the hydraulic cylinder and in the opposite direction by said reaction diaphragm.

2. In a booster unit for a hydraulic pressure system including a power cylinder and a hydraulic cylinder associated therewith, a piston reciprocable in said hydraulic cylinder having a longitudinal passage therethrough and a frusto-conical valve' seat provided at the forward end of said passage, a ball check valve disposed at-the front of the piston and arranged to seat on the confluence of said passage and said frusto-conical valve seat to control said passage, a retainer cap surrounding said ball check valve having an opening in the end wall thereof, a compression spring confined between the end wall of said cap and said ball check valve to urge said ball check valve towards its seat, a pressure transmitting rod concentric with the piston and connected thereto to transmit force from the power cylinder to said piston, said piston having a transverse slot in the rear portion thereof, a member arranged to hold said ball check valve open in retracted position of said piston, said member lying in the slot in said piston and having a portion extending through said passage to contact said ball check valve and also having rearwardly extending forks straddling said pressure transmitting rod, said member being axially movable with respect to said piston and said ball check valve in seated position, spring means urging said piston to released position, and stop means acting through said member to hold said ball check valve oil its seat while said piston is in retracted position.

3. In a booster unit for a hydraulic pressure system including a power cylinder and a hydraulic cylinder associated therewith, a piston reciprocable in said hydraulic cylinder having a longitudinal passage therethrough and a frusto-conical valve seat provided at the forward end of said passage, a ball check valve disposed at the front of the piston yieldably urged to seat on the confluence of said passage and said frustoconical valve seat to control said passagga pressure transmitting rod concentric with the piston and connected thereto to transmit force from the power cylinder to said piston, said piston having a transverse slot in the rear portion thereof, a member arranged to hold said ball check valv, open in retracted position of said piston, said member lying in the slot in said piston and having a portion extending through said passage to contact said ball check valve and also having rearwardly extending forks straddling said pressure transmitting rod, said member being axially movable with respect to said piston and said ball check valve in seated position, spring means urg- 7 ing said piston to released position, and stop means acting through said member to hold said ball check valve of! its seat while said piston is in retracted position.

4. A booster unit for a hydraulic brake system comprising a power cylinder having a casing and a. pressure responsive member movable therein under the influence of a, difl'erential air pressure, an auxiliary master cylinder disposed at the front of said power cylinder, a pair of oppositely reciprocable pistons carried in said auxiliary master cylinder, a pressure transmitting rod connected to said pressure responsive member in said power cylinder and arranged to pass auxiliary master cylinder, said valve means being arranged to control operation of said power cylinder, a connection between said lever and said valve means which enables said lever to operate said valve means and which is adjustable to vary the distance between the valve 8 meansandthepartoftheleverwhich K, the valve means. and a reaction diaphragm associated with said valve means and connected to said lever to exert a force on said lever pr p rtional to the force developed in the power cylinder, said lever being urged in one direction by said one of said pistons in the hydraulic cylinder and in the opposite direction by said reaction diaphragm.

EARL R. PRICE.

REFERENCES CITED The following references are of record in the file of this patent:

unrrap STATES PArsiN'rs Number Name Date 2,223,424 Main Dec. 3, 1940 2,246,140 Main June 17, 1941 2,260,490 Stelzer Oct. 28, 1941 2,308,460 Btelzer Jan. 12, 1943 2,374,545 Ingres Apr. 24, 1945 2,381,989 Stelzer Aug. 14, 1945 2,406,328 Gunderson Aug. 27,1946 2,440,654 Elliott Apr. 27, 1948 

